This invention relates generally to on-board emission control systems for internal combustion engine powered motor vehicles, e.g., evaporative emission control systems, and more particularly to an emission control valve, such as a canister purge solenoid (CPS) valve for an evaporative emission control system.
It is believed that a known on-board evaporative emission control system comprises a vapor collection canister that collects fuel vapor emitted from a tank containing volatile liquid fuel for the engine, and a CPS valve for periodically purging collected vapor to an intake manifold of the engine. It is believed that, in a known evaporative system control system, the CPS valve comprises a solenoid that is under the control of a purge control signal generated by a microprocessor-based engine management system. It is believed that a known purge control signal is a duty-cycle modulated square-pulse waveform having a relatively low operating frequency, e.g., in the 5 Hz to 20 Hz range. It is believed that the modulation may range from 0% to 100%. This means that for each cycle of the operating frequency, the solenoid is energized for a certain percentage of the time period of the cycle. It is believed that as this percentage increases, the time for which the solenoid is energized also increases, and therefore so does the purge flow through the valve. Conversely, it is also believed that the purge flow decreases as the percentage decreases.
During the xe2x80x9conxe2x80x9d time of the duty cycle, an armature of the solenoid travels full stroke. During the xe2x80x9coffxe2x80x9d time of the duty cycle, the armature is returned to its normal position under the bias of a spring engaging the armature. Movement of the armature by the duty-cycle modulated square-pulse wave creates a pulsating noise level that is believed to be unacceptable to users of the valve.
The present invention provides a valve assembly for regulating a fluid flow. The valve assembly comprises a body having a passage extending between a first port and a second port, a seat defining a portion of the passage, a member movable with respect to the seat, an actuator moving the member from the first configuration to the second configuration, and a damper movable with respect to the actuator and located at a radial gap between the member and the actuator. The member moves generally along an axis between a first configuration prohibiting fluid flow through the seat and a second configuration permitting fluid flow through the seat. The member includes a first portion adapted to sealingly engage the seat in the first configuration, and a second portion extending along the axis between a first section that is distal from the first portion and a second section that is fixed to the first portion. The actuator has an aperture extending along the axis and generally receiving the second portion. The aperture includes a first segment generally guiding movement of the first section, and a second segment generally guiding movement of the second section.
The present invention also provides a method of attenuating impact in a valve assembly for regulating a fluid flow. The valve includes a seat that defines a portion of a passage for the fluid flow, a valve movable along an axis with respect to the seat, and an actuator that moves the valve between a first configuration that prohibits the fluid flow through the seat and a second configuration that permits the fluid flow through the seat. The method comprises installing a damper movable with respect to the actuator and located at a radial gap between the valve and the actuator.
The present invention further provides a method of regulating a fluid flow with a valve. The valve includes a seat that defines a portion of a passage for the fluid flow, a valve movable along an axis with respect to the seat, and an actuator that moves the valve between a first configuration that prohibits the fluid flow through the seat and a second configuration that permits the fluid flow through the seat. The method comprises operating the actuator with a pulse-width modulated signal, and generating no more than 35 decibels of sound at an ambient temperature of approximately 20 degrees Celsius.